Multiple Unit Large Volume in situ Filtration System Protocol

James K.B. Bishop

Many of the procedural details for sample handling, sample splitting, blank control, etc. are published. See Bishop et al. (1985) for a description of sample processing schemes.

MULVFS Procedures

Cast documentation

Casts will be identified by standard operation number, date, time of start of cast, filtration starting (time, lat., long.), filtration ending (time. lat., long.), and time of end of cast. Samples in each cast will be identified by nominal wire out depth, pump number, filter holder number, and volume of water filtered.

Depth history of samples determined by real time telemetry of pressure at two sampling locations as well as by internally recording Applied Microsystems STD located at deepest part of the cast.

Pump handling

Where practical, pumps will be covered with plastic between stations; they will be rinsed with fresh water immediately prior to and after each cast.

Filter holder handling

Filter holders and components will be detergent cleaned and acid leached prior to each cruise. They will be rinsed with Milli Q water after each use. They will be covered with plastic at all times until just prior to immersion in the ocean. Plastic covers will be replaced immediately upon recovery.

Sample handling

All MULVFS samples will be processed in a laminar flow clean bench aboard ship. Non- contaminating gloves, subsample templates, and tweezers will be used.

Once subsampling is complete the samples are oven dried at 60-70 degrees C for 1-2 days. This procedure is described by Bishop et al. (1985). They are stored dry in clean polyethylene bags.

MULVFS Filters

Filter types

We use a series of standard filter types in each sample: 53 um Polyester screen, and 2 identical Whatman QM/A quartz fiber filters (pore size is approximately 1 um). The Polyester screened sample is operationally defined as the >53 um fraction, the two QM/A filters are defined as the 1û53 and <1 um fractions, respectively. The latter designation is not quantitative since only a fraction of submicron material is retained by the filter. We will endeavor to compare our estimates of particulate organic matter using these filters with that from Whatman GF/F glass fiber filters, which are frequently used for particulate carbon work. Whatman GF/F's are precluded for our work because they have high and variable major ion and trace metal blanks. Additional efforts to better characterize the submicron organic fraction are in development stages at this time.

Blanks

Filter blanks are determined using unused and process blank filters A process blank filter is one which is deployed at depth on a pump but has no water pumped through it. This filter is processed in an identical way to samples. Process blanks will be obtained at least once every other station. One unused filter set will be retained for blank purposes at least once every 30 samples.

Analysis Protocols

Large particle density and size distributions

>53 um particle size distributions are determined by optical color (8 bit RGB) scanner. Samples within polyethylene bags are imaged at 300 dpi (dots/inch; 1 dpi is approximately 70 um). Scanner is calibrated with a known photographic gray optical density standard. This method quantifies mass loading of 53 um Polyester filters which allows subsampling at sea.

Microscopy

Selected samples will be analyzed by light microscopy and SEM when chemical data indicate important features in the particle field or when major issues need to be resolved regarding estimates of particle flux.

Dry weight

This procedure is discussed in Bishop and Edmond .(1976). Typical quantities of particulate matter obtained in each MULVFS sample are 100-200 mg (1-53 um fraction) and 10's to 100 mg (>53 um fraction). 53 um Polyester, and 1 um microquartz filters are preweighed to better than 1 mg. Unused reference filters are used to track variations in room humidity during weighing. These control filters also track variations in dry weight due to humidity differences between the time the filters were originally weighed and after the samples are obtained. A humidity controlled and particle-free environment is used for this work. Samples must be rinsed to reduce the sea salt content ten-fold in order to get decent dry weights. This results in potential loss of organics and labile elements. (This effect is no more than 15% for bulk carbon, Bishop and Edmond, 1976). UNRINSED SUBSAMPLES MAY BE OBTAINED. The contribution of sea salt to dry weight values are corrected for by analyzing Na. Of the major ions (Na, Mg, K and Ca), Na is discriminated against by organisms and therefore is the best estimator of sea salt.

C, N, S

Samples are fumed with 12N HCl ( to remove carbonates) in closed container overnight. Carlo Erba elemental analyzer: standards and analyzer blanks by usual procedures. One in every ten samples is repeated, a reference sample is run one each run of 50 samples and standards. >53 um organic matter is estimated gravimetrically by subtracting inorganic species from dry weight. Nitrogen cannot be estimated on nitex samples without mechanical removal of material from the filter. Sea salt sulfur is determined by Na analysis.

Na, Ca, Mg, K

0.6N HCl leach, at 60 degrees C overnight, followed by separation (Nuclepore filtration) of leachate and remnant filter material. Analysis by flame atomic absorption (or plasma emission). Procedures are standard. Quality control for major ion analysis is the parallel analysis of a sea water sample of known salinity as well as through 1:10 repeat analysis of samples and reference sample. Na, Mg, K, and Ca are conservative in seawater to better than 1%. Methodology is described in Bishop et al. (1977).

Sr

Determined on major ion leach solutions either by flame AA, ICP-MS, or GFAAS. Methodology is described in Bishop et al. (1977).

Calcium carbonate

At least 90% of Ca (in excess of sea salt) is calcium carbonate (Bishop et al., 1977). We plan to use coulometric analyzers to determine inorganic carbon directly in several profiles to better calibrate this percentage.

P

Phosphorus is released from particles to solution by a three step persulphate oxidation process and analyzed colorimetrically. Methodology is described in Bishop et al. (1977), but may be improved. QC as for other samples.

Si (opal)

53 um nitex samples are leached in 1M NaCO overnight. After filtration, samples are neutralized with HCl and analyzed using the standard nutrient method (Bishop et al., 1977). 1-53 um opal is hard to do on quartz fiber filters, but has been estimated gravimetrically (Bishop et al., 1977). We will try to estimate opal by germanium analysis (Ge:Si in opal is constant; Ge is probably not a contaminant of microquartz filters). Methodology will be developed for the ICP-MS. Failing this we plan to collect 0.4 um Nuclepore filter samples using the parallel sampling capabilities of MULVFS. These filters would be leached and analyzed as above.

Al

Total digest of sample followed by ICP-MS of AlO+, or GFAAS. L-DEO presently has established methodology for sediment and sediment trap analysis. We will adapt these techniques to water column particulate matter samples. QC as for other elements.

Ba

Major ion leach solutions are analyzed by GFAAS method of Bishop (1990) or by ICP-MS. Results are representative of total barium sulfate (the dominant phase) and absorbed/ion-exchangeable barium. QC is the same as for major ions. Blanks are controlled by analysis of unused and procedural blanks as well as through analysis of paired quartz filter (>1 vs. 1-53 um size fraction).

Reactive Mn

Archived major ion leach solutions are analyzed by GFAAS method of Bishop and Fleisher (1987) or by ICP-MS. All `reactiveÆ Mn is quantified by this method. QC is the same as for major ions.

Leachable Fe, Cu

Analysis scheme similar to that for Mn by GFAAS. We will develop and test methodology ensure complete recovery of leachable elements.

Pb

Analysis by GFAAS (platform) or by ICP-MS. GFAAS methodology is standard. QC is identical to that for Ba, Mn, Cu.

Literature Cited

Bishop, J.K.B. and Edmond, J.M. (1976).
A new large volume filtration system for the sampling of oceanic particulate matter. Journal of Marine Research, 34: 181-198.
Bishop, J.K.P., Edmond, J.M., Ketten, D.R., Bacon, M.P., and Silker, W.B. (1977).
The chemistry, biology and vertical flux of particulate matter from the upper 400 m of the equatorial Atlantic Ocean. Deep-Sea Research, 24: 511-548.
Bishop, J.K.B., Schupack, D., Sherrell, R.M., and Conte, M. (1985).
A Multiple Unit Large Volume in-situ Filtration System (MULVFS) for sampling oceanic particulate matter in mesoscale environments. pp. 155-175 In: A. Zirino (ed.), Mapping Strategies in Chemical Oceanography, Advanced in Chemistry Series, Vol. 209, American Chemical Society, Washington, D.C.
Bishop, J.K.B. (1986).
The correction and suspended mass calibration of Sea Tech transmissometer data. Deep-Sea Research, 33: 121-134.
Bishop, J.K.B. and Fleisher, M.Q. (1987).
Particulate manganese dynamics in Gulf Stream warm-core rings and surrounding waters of the N.W. Atlantic. Geochimica et Cosmochimica Acta, 51(10): 2807-2826.
Bishop, J.K.B. (1990).
Determination of Barium in seawater using vanadium/silicon modifier and direct injection graphite furnace atomic absorption spectrometry. Analytical Chemistry, 62: 553-557.